Y_(2)O_(3)含量对TC4表面WC增强钛基激光熔覆层组织与摩擦学性能的影响

Effects of Y_(2)O_(3)Content on Microstructure and Tribological Properties of WC-reinforced Ti-based Coatings on TC4 Surfaces

目的增加航空TC_(4)合金的安全服役寿命。方法采用同轴送粉激光熔覆技术在其表面制备了TC_(4)+Ni-MoS_(2)+WC+xY_(2)O_(3)(x=0%、1%、2%、3%、4%,质量分数)耐磨复合涂层,利用着色渗透探伤、XRD、SEM、EDS、EBSD和TEM等多种检测手段和设备,分析了Y_(2)O_(3)添加对涂层组织与摩擦学性能的影响规律。结果3%Y_(2)O_(3)涂层的成形质量最优,所有涂层生成相相同,主要由TiC、Ti_(2)Ni、Ti_(2)S、基体β-Ti以及未熔WC组成。Y_(2)O_(3)与TiC、Ti_(2)S、Ti_(2)Ni之间形成了共格依附生长关系,所有涂层中均有效合成了TiC-Ti_(2)S、TiC-Ti_(2)Ni和Ti_(2)S-Ti_(2)Ni共格复合结构相。随着Y_(2)O_(3)含量增大,基体显露面积增加,其余物相逐步细化、团聚并沿晶界连续生长。所有涂层的显微硬度均高于TC_(4)基材,大小与Y_(2)O_(3)含量呈负相关变化。所有涂层的摩擦因数均高于基材,磨损率均低于基材,摩擦因数和磨损率随着Y_(2)O_(3)含量增加,出现了先降低后升高的变化规律,其中3%Y_(2)O_(3)涂层的摩擦因数最低(μ=0.4813),耐磨性(3.55×10^(4)mm^(3)/(N·m))和磨损面质量(Ra=21.24μm)最优。结论适量Y_(2)O_(3)有助于改善涂层的成形质量,Y_(2)O_(3)添加并未影响涂层物相种类,且可作为异质形核基底细化相互依附生长的TiC-Ti_(2)S-Ti_(2)Ni共格结构相,除基体相外,Y_(2)O_(3)易吸引其余物相在涂层晶界处钉扎;Y_(2)O_(3)含量增加不能增大涂层显微硬度,所有涂层均不具备减摩性能,但耐磨性均优于TC_(4)基材,适量Y_(2)O_(3)添加可使涂层综合摩擦学性能达到最优。

To enhance the surface mechanical properties and extend the safe service life of aerospace TC_(4)alloy,a composite coating of TC_(4),Ni-MoS_(2),WC,and Y_(2)O_(3)powders was prepared on the surface of TC_(4)alloy using laser cladding,which improved the microhardness and wear resistance of the substrate surface.This study investigated the effect of Y_(2)O_(3)content on the microstructure,hardness,and tribological properties of the coating.Using a Laser TruDisk4002 laser under argon protection,wear-resistant composite coatings of TC_(4)+Ni-MoS_(2)+WC+xY_(2)O_(3)(x=0wt.%,1wt.%,2wt.%,3wt.%,4wt.%)were prepared on a TC_(4)alloy substrate.The coating was observed with a scanning electron microscope(SEM).Phase identification was conducted by X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).The microhardness distribution of the coating was studied with a Vickers microhardness tester.The friction and wear properties of the coating were tested with a dry friction tester,and the wear morphology was analyzed with a non-contact white light interferometer profilometer.Additionally,the coherent relationships between the phases in the coating were calculated according to the Bramfitt’s two-dimensional lattice misfit theory.Results showed that the 3wt.%Y_(2)O_(3)coating exhibited the best forming quality.As the Y_(2)O_(3)content increased,the coating thickness increased from 0.975 mm to 1.447 mm.The cladding layer mainly consisted of TiC,Ti_(2)Ni,Ti_(2)S,matrixβ-Ti,and unmolten WC.The addition of Y_(2)O_(3)did not change the types of phases formed in the coating.According to the Bramfitt two-dimensional lattice misfit calculations,the misfit percentages between and,and,and.were 4.273%,3.671%,and 1.974%,respectively.Therefore,a coherent attachment growth relationship was formed between Y_(2)O_(3)and TiC,Ti_(2)S and Ti_(2)Ni,and coherent composite structures of TiC-Ti_(2)S,TiC-Ti_(2)Ni,and Ti_(2)S-Ti_(2)Ni were effectively synthesized in all coatings.With the increase of Y_(2)O_(3)content,the exposed area of the matrix increased,and the remaining phases gradually refined,aggregated,and grew continuously along the grain boundaries.The microhardness of all coatings was higher than that of the TC_(4)substrate,with the 3%Y_(2)O_(3)content coating having a hardness of 563.14HV0.5,which was a 39.89%improvement compared with the substrate.All coatings underwent dry friction tests under load of 10 N,duration of 60 min,speed of 200 r/min,and room temperature conditions.Among them,the 3%Y_(2)O_(3)-containing coating exhibited the lowest friction coefficient(μ=0.4813),the best wear resistance(3.55×10^(4)mm^(3)/(N·m)),and the optimal surface roughness(Ra=21.24μm).Research finds that an appropriate amount of Y_(2)O_(3)helps improve the forming quality of the coating,and its addition does not affect the types of phases in the coating.Moreover,it can serve as a heterogeneous nucleation substrate,promoting the mutual growth of TiC-Ti_(2)S-Ti_(2)Ni coherent structural phases.Besides the matrix phase,Y_(2)O_(3)also attracts other phases at the grain boundaries of the coating.However,an increase in Y_(2)O_(3)content does not increase the microhardness of the coating,and all coatings lack friction reduction performance,but their wear resistance is superior to that of the TC_(4)substrate.Proper addition of Y_(2)O_(3)can optimize the overall tribological performance of the coating.